The invention relates to a continuous H2 production system in which photosynthetic O2 evolution and H2 photoproduction are separated physically in two separate bioreactors, wherein the first bioreactor operates as a sulfur chemostat to generate photosynthetically competent and active cells, which are continuously fed to a second photobioreactor wherein the culture produces H2 under anaerobic conditions, does not accumulate toxic levels of fermentation products, and is continuously replenished by fresh cells from the first chemostat to prevent complete inactivation of H2-production activity and claims benefit of the Oct. 1, 2002 filing date of provisional application P60/414,993.